The reason for his actions? He was there to "self-investigate" an online conspiracy theory now handily known to those online as "Pizzagate," one of the weirdest, most grotesque Hillary Clinton conspiracy theories ever circulated (which is saying something).

But to the casual news consumer, this may be the first they've heard of Pizzagate. So, if this is you, here's the backstory.

The Conspiracy

"Pizzagate" is an ongoing circulated conspiracy theory that Democratic operatives, including 2016 Democratic presidential nominee Hillary Clinton, use Comet and the Clinton Foundation as a front for a global pedophilia ring which may or may not include some satanic rituals.

Its start, as Craig Silverman explains at Buzzfeed, was literally a small handful of random people with no evidence whatsoever that gained steam on message boards and social media platforms and was one of the most widely shared fake stories on Reddit (particularly the subreddit "r/The_Donald") and Facebook during the late stages of the presidential campaign.

The Spread

After the leaks of Clinton advisor John Podesta's emails, trolls began circulating excerpts they claimed referred to the (again, nonexistent) child trafficking ring.

Throwing gasoline on this very dangerous fire have been sites like the tin-foil hat clearinghouse Info Wars, which has discussed the conspiracy at length (when not talking about Clinton's smell) and Breitbart, the conservative news outlet that was formerly run by Donald Trump's senior advisor Steve Bannon, which shared tweets like:

All of this has been churned through the usual places, including, as The Daily Beast notes, a recently-banned Reddit community dedicated to the conspiracy.

One more person amplifying the outlandish theory is the son of Trump's incoming National Security Adviser Gen. Michael Flynn (who himself has a penchant for believing Clinton-related child trafficking conspiracy theories).

After another "Pizzagate" conspiracy theorist sent out a tweet that contained a fake quote from the D.C. police chief, Flynn's son regurgitated the tweet with a "prove me wrong!" sentiment.

For the record, the D.C. police said in a statement on Sunday night, "During a post arrest interview this evening, the suspect revealed that he came to the establishment to self-investigate 'Pizza Gate' (a fictitious online conspiracy theory)."

The Fallout

To read the accounts from mainstream media, something like this was a long time coming. As the conspiracy has circulated, the pizzeria has found itself the target of repeated harassment and threats.

Protesters even confronted Comet's owner, James Alefantis, at the restaurant at one point.

After Sunday's incident, Alefantis told the New York Times, "What happened today demonstrates that promoting false and reckless conspiracy theories comes with consequences. I hope that those involved in fanning these flames will take a moment to contemplate what happened here today, and stop promoting these falsehoods right away.”

With confirmation that the shooter, Edgar M. Welch, said he was there to look into the false claims, conspiracy theorists are now claiming Sunday's incident was a "false flag" — a manufactured incident — that will be utilized to force censorship on "independent news."

Other business owners and residents in Comet's neighborhood expressed how they've feared something like what happened Sunday to the Washington Post.

Matt Carr, owner of Little Red Fox, a small cafe next door to Comet, told the Post of threats even his establishment has received and added, “This was our worst fear, that someone would read all this and come to the block with a gun. And today it happened.”

So there we have it: An entirely false conspiracy theory concocted using cherry-picked quotes from otherwise innocuous stolen emails has led an armed man to fire a gun an otherwise unremarkable pizzeria.

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